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SSDs have become fast, except in the cloud

(databasearchitects.blogspot.com)
589 points greghn | 2 comments | 20 Feb 24 16:59 UTC | HN request time: 0.499s | source
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pclmulqdq ◴[20 Feb 24 17:22 UTC] No.39443994[source]▶
This was a huge technical problem I worked on at Google, and is sort of fundamental to a cloud. I believe this is actually a big deal that drives peoples' technology directions.

SSDs in the cloud are attached over a network, and fundamentally have to be. The problem is that this network is so large and slow that it can't give you anywhere near the performance of a local SSD. This wasn't a problem for hard drives, which was the backing technology when a lot of these network attached storage systems were invented, because they are fundamentally slow compared to networks, but it is a problem for SSD.

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jsnell ◴[20 Feb 24 17:31 UTC] No.39444096[source]▶
According to the submitted article, the numbers are from AWS instance types where the SSD is "physically attached" to the host, not about SSD-backed NAS solutions.

Also, the article isn't just about SSDs being no faster than a network. It's about SSDs being two orders of magnitude slower than datacenter networks.

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pclmulqdq ◴[20 Feb 24 17:35 UTC] No.39444161[source]▶
It's because the "local" SSDs are not actually physically attached and there's a network protocol in the way.
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hathawsh ◴[20 Feb 24 21:00 UTC] No.39446840[source]▶
That seems like a big opportunity for other cloud providers. They could provide SSDs that are actually physically attached and boast (rightfully) that their SSDs are a lot faster, drawing away business from older cloud providers.
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solardev ◴[20 Feb 24 21:51 UTC] No.39447445[source]▶
For what kind of workloads would a slower SSD be a significant bottleneck?
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1. lolc ◴[20 Feb 24 23:39 UTC] No.39448439[source]▶
I tend some workloads that transform data grids of varying sizes. The grids are anon mmaps so that when mem runs out, they get paged out. This means processing stays mostly in-mem yet won't abort when mem runs tight. The processes that get hit by paging slow to a crawl though. Getting faster SSD means they're still crawling but crawling faster. Doubling SSD throughput would pretty much half the tail latency.
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2. solardev ◴[21 Feb 24 00:08 UTC] No.39448632[source]▶
I see. Thanks for explaining!